Evaluating carbon storage, timber harvest, and habitat possibilities for a western Cascades (US) forest landscape

Forest policymakers and managers have long sought ways to evaluate the capability of forest landscapes to jointly produce timber, habitat, and other ecosystem services in response to forest management. Currently, carbon is of particular interest as policies for increasing carbon storage on federal lands are being proposed. However, a challenge in joint production analysis of forest management is adequately representing ecological conditions and processes that influence joint production relationships. We used simulation models of vegetation structure, forest sector carbon, and potential wildlife habitat to characterize landscape-level joint production possibilities for carbon storage, timber harvest, and habitat for seven wildlife species across a range of forest management regimes. We sought to: (1) characterize the general relationships of production possibilities for combinations of carbon storage, timber, and habitat; and (2) identify management variables that most influence joint production relationships. Our 160,000-ha study landscape featured environmental conditions typical of forests in the western Cascade Mountains of Oregon (US). Our results indicate that managing forests for carbon storage involves tradeoffs among timber harvest and habitat for focal wildlife species, depending on the disturbance interval and utilization intensity followed. Joint production possibilities for wildlife species varied in shape, ranging from competitive to complementary to compound, reflecting niche breadth and habitat component needs of species examined. Managing Pacific Northwest forests to store forest sector carbon can be roughly complementary with habitat for Northern Spotted Owl, Olive-sided Flycatcher, and Red Tree Vole. However, managing forests to increase carbon storage potentially can be competitive with timber production and habitat for Pacific Marten, Pileated Woodpecker, and Western Bluebird, depending on the disturbance interval and harvest intensity chosen. Our analysis suggest that joint production possibilities under forest management regimes currently typical on industrial forest lands (e.g., 40- to 80-year rotations with some tree retention for wildlife) represent but a small fraction of joint production outcomes possible in the region. Although the theoretical boundaries of the production possibilities sets we developed are probably unachievable in the current management environment, they arguably define the long-term potential of managing forests to produce multiple ecosystem services within and across multiple forest ownerships.

长期以来，森林政策制定者与森林管理者始终致力于探索可行方法，以评估森林景观在响应森林经营活动时，能否联合产出木材、野生动物栖息地及其他生态系统服务。当前，随着提升联邦土地碳储量的相关政策陆续提出，碳储量相关研究备受关注。然而，在森林经营联合生产分析中，一项核心挑战在于如何充分表征影响联合生产关系的生态状况与过程。本研究依托植被结构、森林部门碳及潜在野生动物栖息地模拟模型，针对多种森林经营模式下的7种野生动物，刻画了研究景观尺度上碳储量、木材采伐与野生动物栖息地的联合生产潜力。我们的研究目标包括：(1) 刻画碳储量、木材与栖息地组合的通用生产可能性关系；(2) 识别对联合生产关系影响最为显著的经营变量。本研究的16万公顷样区，其环境条件与美国俄勒冈州喀斯喀特山脉西部的典型森林相一致。研究结果表明，为碳储量目标开展的森林经营，会根据所采用的干扰周期与利用强度，在木材采伐与重点野生动物栖息地之间产生权衡取舍。不同野生动物物种的联合生产潜力关系形态各异，涵盖竞争关系、互补关系至复合关系，这反映了所研究物种的生态位宽度与栖息地组分需求差异。在太平洋西北地区的森林经营中，为提升碳储量而开展的管理活动，与北方斑点鸮(Northern Spotted Owl)、橄榄色霸鹟(Olive-sided Flycatcher)以及红树鼠(Red Tree Vole)的栖息地需求大致呈互补关系。然而，根据所选的干扰周期与采伐强度，为提升碳储量而开展的森林经营，可能与木材生产以及太平洋貂(Pacific Marten)、黑啄木鸟(Pileated Woodpecker)和西方蓝鸲(Western Bluebird)的栖息地需求形成竞争关系。本研究分析显示，当前工业用材林用地普遍采用的森林经营模式（例如，采用40至80年轮伐期并保留一定林木以支撑野生动物）所对应的联合生产潜力，仅占该区域可实现联合生产成果的极小一部分。尽管我们构建的生产可能性集的理论边界在当前经营环境下或许难以达成，但它们无疑界定了在多森林权属内部及跨森林权属开展森林经营，以提供多种生态系统服务的长期潜力。